A number of devices exist that may be used to detect tamper events in devices or boxes that utilize optical fibers for internal and external communication. One such device is illustrated in FIG. 1. FIG. 1 shows a cross section view of a tamper sensing device 10. The device 10 comprises a case 12 that has a top 14 wall, a bottom wall 16 and side walls 18 and 20 which define an enclosed volume (v). Extending into the volume is an input optical fiber 22 and an output optical fiber 24. A light path 26 exists between the input and output optical fibers 22 and 24. An input lens 28 exists adjacent the input optical fiber 22 and an output lens 30 exists adjacent the output fiber 24. The input and output lenses 28 and 30 collimate the light path 26 that exists between the input and output optical fibers 22 and 24. A case screw 32 having a screw head 34 and screw body 36 is inserted into the top wall 14 of the case 12 so that part of the screw body 36 is in the volume (v) and blocks part of the light path 26. The device is capable of attenuating the amount of light that reaches the second optical fiber 24 allowing the device to sense a tamper event. FIG. 2 shows the amount of light received by the output fiber 24 when the case screw 32 partially blocks the light path 26 as shown in FIG. 1. If someone tries to tamper with the device 10 by trying to remove the case screw 32, the case screw 32 will change positions and affect the amount of light reaching the output optical fiber 24. The problem with the tamper sensing device 10 is that after removing the case screw 32, the case screw 32 can be reset to conceal the tamper event.
FIG. 3 shows another tamper sensing device 50 used to detect a tamper event within an optical system. Device 50 shows a case screw 52 that has a screw head 54 and a screw body 56 and a hole 58 through the screw body 56. A fiber optic cable 60 travels through the hole 58, lithe screw 52 is removed, the fiber optic cable 60 breaks. However, because the tamper event breaks the fiber optic cable 60 it also prevents data from traveling over cable 60 which is not ideal.
FIG. 4 is an exploded perspective view of an example environment 70 in which a tamper sensing device 72 such as the devices shown in FIGS. 1 and 3 is used. The tamper sensing device 72 sits on a support structure 74 inside of a box 76 that has a lid 78. A case screw 80 is used secure the lid 78 onto the box 76 through a screw hole 82 that extends into device 72. The box 76 contains a fiber optic system. The tamper sensing device 72 detects if someone removes or tries to remove the screw 80 to get inside the box 76.